Selecting output destinations for kernel messages

ABSTRACT

Methods, apparatus and computer program products implement embodiments of the present invention to identify, in a given kernel source code file for the operating system kernel, a given PRINTK function call having a corresponding message text, the given kernel source code file having a kernel source code file name, calculate a configuration checksum, to assign, add, and store the respective destination and a key comprising the configuration checksum, to load, receive, and identify the name of a given source code file, and to determine, based on the identified name and the text string, a computed destination for the system message by calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry. in the identified entry.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No. 14/010,725, filed Aug. 27, 2013, which is related to U.S. patent application titled “Preprocessing Kernel Print Commands”, filed on even date with the present application, and which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to operating system kernels, and specifically to a method of controlling the output destination for individual error/log messages based on a downloadable configuration file.

BACKGROUND

Operating systems are computer programs which manage the way software applications utilize the hardware of computer systems. A fundamental component of operating systems is the operating system kernel (also referred to herein as a “kernel”), which provides secure computer system hardware access to software applications executing on the computer system. Since accessing the hardware can be complex, kernels may implement a set of hardware abstractions to provide a clean and uniform interface to the underlying hardware. The abstractions provided by the kernel provide software developers easier access to the hardware when writing software applications.

The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.

SUMMARY

There is provided, in accordance with an embodiment of the present invention a method, including identifying, by a processor, in a given kernel source code file for the operating system kernel, a given PRINTK function call having a corresponding message text, the given kernel source code file having a kernel source code file name; calculating, using the kernel source code file name and the corresponding message text, a configuration checksum; assigning a respective destination to the configuration checksum; adding a record to a configuration file stored on a storage device coupled to the processor; storing, to the added record, the respective destination and a key comprising the configuration checksum; loading the record to an entry in a configuration table stored in a memory coupled to the processor; receiving, by the processor, a request to generate a system message comprising a text string; identifying a name of a source code file storing a function call that conveyed the request; and determining, based on the identified name and the text string, a computed destination for the system message by calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry.

Other system and computer program product embodiments are provided and supply related advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a block diagram that schematically illustrates a storage system, in accordance with an embodiment of the present invention;

FIG. 2 is a block diagram of a module of the storage system arranged to use a configuration file to control the output destination of individual kernel log messages, in accordance with an embodiment of the present invention;

FIG. 3 is a table that shows sample entries in the configuration file, in accordance with an embodiment of the present invention; and

FIG. 4 is a flow diagram that schematically illustrates a method for generating kernel log messages, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

In a computer system executing a Linux™ operating system kernel, system information can be logged using the PRINTK function. When calling the PRINTK function, a log message (also referred to herein as message text) and a priority parameter indicating a “log level” can be included in the function call, and the PRINTK function can use the priority parameter to determine an output destination (e.g., a console, a memory buffer or a disk file) for the log message. Each of the output destinations has its own advantages and disadvantages, and the output destination for a particular log level can be set by a programmer when the kernel is compiled.

Embodiments of the present invention provide methods and mechanisms for a computer executing a Linux™ operating system kernel to dynamically select an output destination for a given system message. In some embodiments, a configuration file is created that contains one or more records, wherein each record has a key comprising a checksum value (also referred to herein as a configuration checksum) indicating a given call to the PRINTK function, and a respective destination for a message generated by the given call. As described hereinbelow, the checksum value can be calculated based on a name of a source code file containing the given call to the PRINTK function and message text included as a parameter in the given call.

In operation, the PRINTK function can be modified so that upon being called, the PRINTK function identifies a name of given source code file containing the function, calculates an additional checksum (also referred to herein as a message checksum) based on the identified name and message text received in the function call, and upon identifying an entry in the configuration table having a key matching the message checksum, the PRINTK function can convey the message text to a respective destination retrieved from the identified entry.

FIG. 1 is a block diagram that schematically illustrates a data processing storage subsystem 20, in accordance with an embodiment of the invention. The particular subsystem (also referred to herein as a storage system) shown in FIG. 1 is presented to facilitate an explanation of the invention. However, as the skilled artisan will appreciate, the invention can be practiced using other computing environments, such as other storage subsystems with diverse architectures and capabilities.

Storage subsystem 20 receives, from one or more host computers 22, input/output (I/O) requests, which are commands to read or write data at logical addresses on logical volumes. Any number of host computers 22 are coupled to storage subsystem 20 by any means known in the art, for example, using a network. Herein, by way of example, host computers 22 and storage subsystem 20 are assumed to be coupled by a Storage Area Network (SAN) 26 incorporating data connections 24 and Host Bus Adapters (HBAs) 28. The logical addresses specify a range of data blocks within a logical volume, each block herein being assumed by way of example to contain 512 bytes. For example, a 10 KB data record used in a data processing application on a given host computer 22 would require 20 blocks, which the given host computer might specify as being stored at a logical address comprising blocks 1,000 through 1,019 of a logical volume. Storage subsystem 20 may operate in, or as, a SAN system.

Storage subsystem 20 comprises a clustered storage controller 34 coupled between SAN 26 and a private network 46 using data connections 30 and 44, respectively, and incorporating adapters 32 and 42, again respectively. In some configurations, adapters 32 and 42 may comprise host bus adapters (HBAs). Clustered storage controller 34 implements clusters of storage modules 36, each of which includes an interface 38 (in communication between adapters 32 and 42), and a cache 40. Each storage module 36 is responsible for a number of storage devices 50 by way of a data connection 48 as shown.

As described previously, each storage module 36 further comprises a given cache 40. However, it will be appreciated that the number of caches 40 used in storage subsystem 20 and in conjunction with clustered storage controller 34 may be any convenient number. While all caches 40 in storage subsystem 20 may operate in substantially the same manner and comprise substantially similar elements, this is not a requirement. Each of the caches 40 may be approximately equal in size and is assumed to be coupled, by way of example, in a one-to-one correspondence with a set of physical storage devices 50, which may comprise disks. In one embodiment, physical storage devices may comprise such disks. Those skilled in the art will be able to adapt the description herein to caches of different sizes.

Each set of storage devices 50 comprises multiple slow and/or fast access time mass storage devices, herein below assumed to be multiple hard disks. FIG. 1 shows caches 40 coupled to respective sets of storage devices 50. In some configurations, the sets of storage devices 50 comprise one or more hard disks, which can have different performance characteristics. In response to an I/O command, a given cache 40, by way of example, may read or write data at addressable physical locations of a given storage device 50. In the embodiment shown in FIG. 1, caches 40 are able to exercise certain control functions over storage devices 50. These control functions may alternatively be realized by hardware devices such as disk controllers (not shown), which are linked to caches 40.

Each storage module 36 is operative to monitor its state, including the states of associated caches 40, and to transmit configuration information to other components of storage subsystem 20 for example, configuration changes that result in blocking intervals, or limit the rate at which I/O requests for the sets of physical storage are accepted.

Routing of commands and data from HBAs 28 to clustered storage controller 34 and to each cache 40 may be performed over a network and/or a switch. Herein, by way of example, HBAs 28 may be coupled to storage modules 36 by at least one switch (not shown) of SAN 26, which can be of any known type having a digital cross-connect function. Additionally or alternatively, HBAs 28 may be coupled to storage modules 36.

In some embodiments, data having contiguous logical addresses can be distributed among modules 36, and within the storage devices in each of the modules. Alternatively, the data can be distributed using other algorithms, e.g., byte or block interleaving. In general, this increases bandwidth, for instance, by allowing a volume in a SAN or a file in network attached storage to be read from or written to more than one given storage device 50 at a time. However, this technique requires coordination among the various storage devices, and in practice may require complex provisions for any failure of the storage devices, and a strategy for dealing with error checking information, e.g., a technique for storing parity information relating to distributed data. Indeed, when logical unit partitions are distributed in sufficiently small granularity, data associated with a single logical unit may span all of the storage devices 50.

While such hardware is not explicitly shown for purposes of illustrative simplicity, clustered storage controller 34 may be adapted for implementation in conjunction with certain hardware, such as a rack mount system, a midplane, and/or a backplane. Indeed, private network 46 in one embodiment may be implemented using a backplane. Additional hardware such as the aforementioned switches, processors, controllers, memory devices, and the like may also be incorporated into clustered storage controller 34 and elsewhere within storage subsystem 20, again as the skilled artisan will appreciate. Further, a variety of software components, operating systems, firmware, and the like may be integrated into one storage subsystem 20.

Storage devices 50 may comprise a combination of high capacity hard disk drives and solid state disk drives. In some embodiments each of storage devices 50 may comprise a logical storage device. In storage systems implementing the Small Computer System Interface (SCSI) protocol, the logical storage devices may be referred to as logical units, or LUNs. While each LUN can be addressed as a single logical unit, the LUN may comprise a combination of high capacity hard disk drives and/or solid state disk drives.

Examples of adapters 32 and 42 include switched fabric adapters such as Fibre Channel (FC) adapters, Internet Small Computer System Interface (iSCSI) adapters, Fibre Channel over Ethernet (FCoE) adapters and Infiniband™ adapters.

FIG. 2 is a block diagram of a given module 36 arranged to use a configuration file 60 to control the output destination of individual error messages and log messages, in accordance with an embodiment of the present invention. In embodiments herein, error messages and log messages may collectively be referred to as log messages. Module 36 comprises a processor 62 and a memory 64, and is coupled to a console 66 (e.g., an LCD display).

In operation, processor 62 executes an operating system kernel 68 that comprises a PRINTK function 70. As described supra, PRINTK function 70 can be configured to convey a given log message to a given destination. In the configuration shown in FIG. 2, the destinations comprise console 66, a kernel message buffer 72 in memory 64, an event monitoring application 74 (e.g., a SNMP application) in memory 64 or a kernel log file 76 stored on storage device 50. In some embodiments, PRINTK function 70 may be configured to convey a given log message to a “null” destination (i.e., a “no-op” command).

Examples of kernel log files 76 that can be stored on storage device 50 include, but are not limited to:

-   -   A single system log file. An example of a single system log file         comprises the /var/log/messages file in systems executing a         Linux™ kernel. In some embodiments, the single system log file         may be configured as a first in, first out (FIFO) system-wide         debug log.     -   Multiple system log files. For example, systems executing a         Linux™ kernel may maintain a separate log file for each device         driver executing on the system.

Storage device 50 also stores one or more kernel source code files 80 that a compiler (not shown) can read in order to generate kernel 68. In embodiments described herein, processor 62 can populate a configuration table 78 in memory 64 with data retrieved from configuration file 60 on storage device 50, and PRINTK function 70 can use data stored in configuration table 78 to determine a given destination for a given log message. As described hereinbelow, upon being called, PRINTK function 70 can determine a destination for a given log message by calculating, based on the given log message and a name of a given kernel source file 80 that stores the call to the PRINTK function, a checksum, and then retrieve a destination from an entry in configuration table 78 having a key equal to the calculated checksum.

FIG. 3 is a sample layout of configuration file 60, in accordance with an embodiment of the present invention. Each record in configuration file 60 references a given call to PRINTK function 70 in kernel 68, and comprises a checksum 90, a source file identifier 92, message text 94 and destination flags 96, 98, 100 and 102. Destination flags 96-102 comprise “YES”/“NO” values that determine one or more given destinations for a given instance of PRINTK function 70 referenced by a given checksum 90. For a given record in the configuration file having a given message text 94:

-   -   If flag 96 is set (i.e., stores “YES”), then PRINTK function 70         conveys the given message text to kernel log file 76.     -   If flag 98 is set, then PRINTK function 70 conveys the given         message text to kernel message buffer 72.     -   If flag 100 is set, then PRINTK function 70 conveys the given         message text to console 66.     -   If flag 102 is set, then PRINTK function 70 conveys the given         message text to event monitoring application 74.

In the following example, the first record in configuration file 60 comprises a given call to PRINTK function 70 that will convey “%s-version %s\n” to kernel message buffer 72, and references the following source code statement in source code file 80 “kernel_(—)1.c”:

-   -   printk(KERN_INFO “%s-version %s\n”,     -   my_driver_string, my_driver_version);

In some embodiments, a given message text 94 may be conveyed to multiple destinations. For example, in the second record in configuration file 60, processor 62 configures PRINTK function 70 to convey “%s Is Disabled\n” to kernel log file 76 and kernel message buffer 72, since flags 96 and 98 are both set.

Processor 62 typically comprises a general-purpose central processing unit (CPU), which is programmed in software to carry out the functions described herein. The software may be downloaded module 36 in electronic form, over a network, for example, or it may be provided on non-transitory tangible media, such as optical, magnetic or electronic memory media. Alternatively, some or all of the functions of processor 62 may be carried out by dedicated or programmable digital hardware components, or using a combination of hardware and software elements.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Python, Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/actions specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the functions/actions specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/actions specified in the flowchart and/or block diagram block or blocks.

Log Message Generation

FIG. 4 is a flow diagram that schematically illustrates a method for generating kernel error and log messages, in accordance with an embodiment of the present invention. In an initialization step 110, processor 62 initializes configuration file 60. While for purposes of descriptive simplicity, embodiments herein describe processor 62 initializing configuration file 60, another computer (not shown) may perform the initialization and convey the initialized configuration file to module 36.

To initialize a given record in configuration file 60, processor 62 can identify, in a given kernel source code file 60, a given PRINTK function call having a corresponding message text 94, the given kernel source code file having a kernel source code file name. Processor 62 can then calculate, using the kernel source code file name and the corresponding message text, a configuration checksum, and assign a respective destination to the configuration checksum. As described supra, the respective destination may comprise console 66, kernel message buffer 72, kernel log file 76, event monitoring application 74 or a null destination. Upon assigning the respective destination to the configuration checksum, processor 62 can add a record to configuration file 60, and storethe respective destination and a key comprising the configuration checksum to the added record.

In a load step 112, processor 62 loads the record added to configuration file 60 (in step 110) to an entry in configuration table 78. If there are multiple records in configuration file 60, then processor 62 loads the records to configuration table 78, so that each record in the configuration file 60 has a corresponding entry in the configuration table.

While embodiments herein describe processor 62 populating configuration table 78 with data stored in configuration file 60, other methods of populating the configuration table are considered to be within the spirit and scope of the present invention. In additional embodiments, processor 62 can receive checksums and respective destinations from an input received via a keyboard (not shown) coupled to module 36. For example, a systems administrator (not shown) can input a command line parameter for kernel 68, the command line parameter comprising a checksum and a respective destination that processor 62 can store to an entry to configuration table 78. Alternatively, processor 62 can present an input screen on console 66, the systems administrator can enter a checksum and a respective destination into the input screen, and the processor can store the entered checksum and respective destination to an entry to configuration table 78.

In a first comparison step 114, processor 62 waits to receive a request to convey a system message (e.g., to convey an operating system kernel log message via a PRINTK function call) from kernel 68. The request comprises parameters such as message text 94 (also referred to herein as a text string) and a priority parameter. As described supra, PRINTK function may be configured with a default destination for each of the priority parameters. The priority parameter typically comprises an integer value between zero and seven, where zero indicates the most critical priority level and seven indicates the least critical priority level. In some embodiments, the priority levels may be defined as follows:

-   -   0. The message indicates that the system is unusable. Also         referred to as KERN_EMERG.     -   1. The message indicates that action must be taken immediately.         Also referred to as KERN_ALERT.     -   2. The message indicates that a critical condition exists. Also         referred to as KERN_CRIT.     -   3. The message indicates that an error condition. Also referred         to as KERN_ERR.     -   4. The message indicates that a warning condition exists. Also         referred to as KERN_WARNING.     -   5. The message indicates that a normal but significant condition         exists. Also referred to as KERN_NOTICE.     -   6. The message is solely informational. Also referred to as         KERN_INFO.     -   7. The message comprises a debug-level message. Also referred to         as KERN_DEBUG.

Upon receiving the request, in an identification step 104, processor 62 identifies a name of a given kernel source code file 80 that contains the PRINTK function call that conveyed the request. While embodiments herein describe a method for processor 62 receiving a request to generate an operating system kernel message, receiving a request to generate other types of system messages is considered to be within the spirit and scope of the present invention. For example, processor 62 may execute a database server application, and the database server application may convey requests to generate a message indicating a status of the database server.

In a calculation step 116, processor 62 calculates, using the identified name and the received message text, a message checksum. In some embodiments processor 62 can identify a path for a directory on storage device 50 that stores the identified source code file, and the processor can calculate the checksum based on the path, the name and the received message text. As described hereinbelow, processor 62 can use the calculated checksum to determine a destination for the received message text.

In a second comparison step 120, processor 62 searches configuration table 78 to identify an entry in the configuration table having a key equal to the calculated checksum. If processor 62 identifies an entry with a key matching the calculated checksum, then in a retrieval step 122, processor 62 retrieves the respective destination from the identified entry, conveys the message text to the retrieved destination in a first convey step 124, and the method continues with step 114.

Returning to step 120, if processor 62 fails to identify an entry in configuration table 78 with a key matching the checksum calculated in step 118, then in a second convey step 126, the processor conveys the received message text to the respective default destination for the priority level indicated by the received priority parameter, and the method returns to step 114.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. 

1. A method, comprising: identifying, by a processor, in a given kernel source code file for the operating system kernel, a given PRINTK function call having a corresponding message text, the given kernel source code file having a kernel source code file name; calculating, using the kernel source code file name and the corresponding message text, a configuration checksum; assigning a respective destination to the configuration checksum; adding a record to a configuration file stored on a storage device coupled to the processor; storing, to the added record, the respective destination and a key comprising the configuration checksum; loading the record to an entry in a configuration table stored in a memory coupled to the processor; receiving, by the processor, a request to generate a system message comprising a text string; identifying a name of a source code file storing a function call that conveyed the request; and determining, based on the identified name and the text string, a computed destination for the system message by calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry.
 2. The method according to claim 1, and comprising identifying a path for a directory storing the source code file, and determining the computed destination based on the path, the name and the text string.
 3. The method according to claim 1, wherein determining the destination comprises calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry.
 4. The method according to claim 1, wherein the request comprises the text string and a priority parameter, and wherein the priority parameter comprises a numeric value indicating a priority level selected from a list comprising a KERN_EMERG priority level, a KERN_ALERT priority level, a KERN_CRIT priority level, a KERN_ERR priority level, a KERN_WARNING priority level, a KERN_NOTICE priority level, a KERN_INFO priority level, and a KERN_DEBUG priority level, and wherein each of the priority levels has a respective default destination.
 5. The method according to claim 4, wherein each of the default and the computed destinations is selected from a list comprising a console, a kernel message buffer in the memory, a kernel log file on the storage device, an event monitoring application executing on the processor and a null destination.
 6. The method according to claim 5, and comprising upon failing to identify an entry in the configuration table having a key equal to the calculated checksum, conveying the received text string to the respective default destination for the priority level indicated by the received priority parameter.
 7. An apparatus, comprising: a memory configured to store a configuration table; a storage device coupled to the memory and configured to store one or more source code files and a configuration file; and a processor coupled to the storage device and configured: to identify, in a given kernel source code file for the operating system kernel, a given PRINTK function call having a corresponding message text, the given kernel source code file having a kernel source code file name, to calculate, using the kernel source code file name and the corresponding message text, a configuration checksum, to assign a respective destination to the configuration checksum, to add a record to the configuration file, to store, to the added record, the respective destination and a key comprising the configuration checksum, to load the record to an entry in the configuration, to receive a request to generate a system message comprising a text string, to identify a name of a given source code file storing a function call that conveyed the request, and to determine, based on the identified name and the text string, a computed destination for the system message by calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry.
 8. The apparatus according to claim 7, wherein the processor is configured to convey the text string to the computed destination.
 9. The apparatus according to claim 7, wherein the processor is configured to identify a path for a directory storing the source code file, and to determine the computed destination based on the path, the name and the text string.
 10. The apparatus according to claim 7, wherein the processor is configured to execute an operating system kernel, and wherein the system message comprises an operating system kernel log message, and wherein the function call comprises the PRINTK function call.
 11. The apparatus according to claim 7, wherein the request comprises the text string and a priority parameter, and wherein the priority parameter comprises a numeric value indicating a priority level selected from a list comprising a KERN_EMERG priority level, a KERN_ALERT priority level, a KERN_CRIT priority level, a KERN_ERR priority level, a KERN_WARNING priority level, a KERN_NOTICE priority level, a KERN_INFO priority level, and a KERN_DEBUG priority level, and wherein each of the priority levels has a respective default destination.
 12. The apparatus according to claim 11, wherein each of the default and the computed destinations is selected from a list comprising a console, a kernel message buffer in the memory, a kernel log file on the storage device, an event monitoring application executing on the processor and a null destination.
 13. The apparatus according to claim 12, wherein upon failing to identify an entry in the configuration table having a key equal to the calculated checksum, the processor is configured to convey the received text string to the respective default destination for the priority level indicated by the received priority parameter.
 14. A computer program product, the computer program product comprising: a non-transitory computer readable storage medium having computer readable program code embodied therewith, the computer readable program code comprising: computer readable program code configured to identify, in a given kernel source code file for the operating system kernel, a given PRINTK function call having a corresponding message text, the given kernel source code file having a kernel source code file name; computer readable program code configured to calculate, using the kernel source code file name and the corresponding message text, a configuration checksum; computer readable program code configured to assign a respective destination to the configuration checksum; computer readable program code configured to add a record to a configuration file stored on a storage device; computer readable program code configured to store, to the added record, the respective destination and a key comprising the configuration checksum; computer readable program code configured to load the record to an entry in a configuration table stored in a memory; computer readable program code configured to receive a request to generate a system message comprising a text string; computer readable program code configured to identify a name of a source code file storing a function call that conveyed the request and computer readable program code configured to determine, based on the identified name and the text string, a computed destination for the system message by calculating, using the identified name and the text string, a message checksum, and identifying, in the configuration table, an entry having a key equal to the message checksum, and wherein the determined destination comprises the respective destination in the identified entry.
 15. The computer program product according to claim 14, and comprising computer readable program code configured to convey the text string to the computed destination.
 16. The computer program product according to claim 14, and comprising computer readable program code configured to execute an operating system kernel, and wherein the system message comprises an operating system kernel log message, and wherein the function call comprises the PRINTK function call. 